on the nature and the volume of communication on the earth and it represents a fast growing business, both in the space and ground segment. Less quantifiable, but potentially equally important, is probably earth observation by satellite in its various forms, ranging from weather observation to military reconnaissance. A second area where SPS development would have a major impact would be in the field of solar-energy conversion, at least as long as photovoltaic conversion is used. The United States has a very ambitious photovoltaic research and development programme, presently funded with approximately $200 million per year. If the cost goals of this programme, namely $0.6-$l/Wpeak for a complete photovoltaic power plant, can be achieved, photovoltaic energy conversion is expected to be used on a very large scale. The United States President has set 1 quad (= 3 x 10" kWh) as the goal for photovoltaic electricity in the year 2000 (9). This goal would require an investment of more than $100 billion in photovoltaic plants, considering only the most favourable locations in the United States and the construction of almost 1000 km2 of photovoltaic collectors. An SPS programme would create an additional market of approximately the same size. European industry would probably only find a large domestic market if Europe participated in an SPS programme. It appears unlikely that European governments and industries would make the huge investment necessary for the development of a large photovoltaic industry if there would be only an export market. A further area where an SPS programme would be a technology driver is in cableless transmission of energy. Even without trying to anticipate the final choice of power-transmission concept (microwave or laser are under discussion) it can be safely assumed that SPS development would bring a tremendous advancement in technologies which are unlikely to come from other (civilian) projects, but which are likely to have a great impact in other areas also. Although the potential technical impact of an SPS development is often understood, most European government agencies have adopted a “wait and see” attitude, waiting for the results of studies in the United States. This attitude does not take into account that the SPS concept is already now motivating research in many areas, e.g., atmospheric and ionospheric sciences, biology, microwave transmission, and space engineering. The SPS Concept Development and Evaluation Program in the United States has shown that as a first step, a broad range of basic and applied research must be conducted. This research should be directed at issues raised by the SPS but is expected to be broadly applicable (10). Waiting for a decision of the United States to start a large scale SPS development programme is likely to imply that Europe would only become a junior partner in any joint activity. 5. CONCLUSIONS The lack of indigenous energy sources in sufficient quantities to support our present industrial and economic system presents Europe with financial and political problems. Although complete independence is hardly feasible or even desirable, there must be very strong interest in reducing our present large dependence on just a few oil-producing countries by developing new domestic energy sources. In the short term, it might be feasible to increase the production and the import of other fossil fuels such as coal and gas, but in order to assure the continuous availability of energy, new energy sources must be developed in Europe. A number of relatively small additional sources are already being developed in Europe, e.g., wind, terres-
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